Lie on a sturdy bench with your knees bent and feet flat. Hold five to 10 pounds dumbbells in each hand and straighten your arms directly over your chest (A). Keeping your palms facing each other, bend your elbows, and slowly lower the dumbbells toward your shoulders until your lower arm is at a 45-degree angle to your upper arm (B). Pause here for two seconds, press back to the starting position. That’s one rep; complete 12.